ESP32CompositeColorVideo

This repository is a fork of Bitluni's ESP32CompositeVideo that adds color in NTSC and PAL by borrowing code from ESP_8_BIT. It also rearranges the code and examples into an Arduino library for ease of use.

See esp32-dali-clock for an example of what this modified code can do.

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At first, I tried Bitluni's ESP32SpaceShooter that implements color in PAL. However, my monitor had a difficult time keeping sync. After some digging, I came across rossumur's ESP_8_BIT which purported to use the Audio Phase Locked Loop capability of the ESP32 to generate a better color signal. Not only that, but it managed to do so for both PAL and NTSC.

Intrigued, I set out to see if I could adapt this code for my own use. But first I had to free the NTSC/PAL code from the ESP_8_BIT project. The code was written very specifically for several different emulators, but I was able to tease out the bits for the Atari which would give me a fixed 336 by 240 pixels of resolution and a 256 color pallete.

I found the relevant code and unsucessfully tried to understand how it worked (I assume magic). Nonetheless, I was able to grasp just enough to make it run standalone without the emulators.

Having done this, I needed a way to draw to the framebuffer. Fortuitously, I found that the framebuffer was compatible with the graphics library Bitluni had already developed.

Examples in this library

The two examples from bitluni's original library have been modified to run in color. They are:

CompositeVideoSimple: renders text, a few lines and an image in color.
CompositeVideo: renders a 3D mesh and display it in color.

Wiring for an Adafruit HUZZAH32:

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Use an alligator clip to connect the pin labeled "GND" on the Adafruit HUZZAH32 to the outside barrel of the RCA plug
Use an alligator clip to connect the pin labeled "A1/DAC1" on the Adafruit HUZZAH32 to the central pin of the RCA plug
Connect the other end of the RCA cable to the yellow jack on your TV or monitor

Bitluni's Blog Posts

Bitluni has written extensively on his projects, I am including links to the relevant blog posts here.

Documentation for Developers

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Drawing colors (compatibility mode):

To maintain compatibility with Bitluni's original ESP32CompositeVideo library, the drawing routines all accept a value from 0 through 54. In the original library, these values specified one of 55 different shades of gray. This version of the library can only show 16 levels of brightness, but in this mode the original range is preserved for compatibility.

Although it limits the number of brightness levels, this library makes up for it by allowing the selection one of sixteen different hues, which are then combined with the brightness values for all subsequent drawing operations. Example:

graphics.setHue(hue);                  // Range: 0-15 (0 means B&W)
graphics.fillRect(x,y,w,h,brightness); // Range: 0-54

Hence, 256 total colors are available: 16 different shades of 16 different hues.

Drawing colors (Atari mode):

Alternatively, you can choose to use Atari colors values by declaring USE_ATARI_COLORS before you include "CompositeGraphics.h"

When this mode is enabled, the color argument to the various functions will take a color from the Atari color palette. This palette is quite convenient because when expressed in hexdecimal, the first nibble indicates one of 16 different hues while the second nibble indicates one of 16 possible values of brightness.

In this mode, all the 256 colors can be expressed directly and graphics.setHue() is not available. This mode will also be more performant. Example:

#define USE_ATARI_COLORS
#include "CompositeGraphics.h"

...

graphics.fillRect(x,y,w,h,color); // Range: 0x00 - 0xFF

Licenses

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